The present invention relates to vehicle seats adapted to be tilted or tipped forwards from their normal driving position in order particularly to liberate access to the rear places if the vehicle is of the so-called "three door" type.
It is directed more particularly, among these seats, to those which comprise a base which can be fastened to the floor of the vehicle, a sitting portion resting on the base through a height-adjustment device and a back rest portion, said seat being mounted to pivot around a transverse axle connected rigidly to the base so as to be tiltable forwards in pulling the rear of the sitting portion.
It relates more particularly also to the case where the height-adjustment device comprises a pair of transversely spaced parallel front racks, a pair of transversely spaced parallel rear racks, two coaxial front pinions with transverse axle fastened to one another by a rigid front cross-piece mounted on the sitting portion and adapted to cooperate with the front racks, two coaxial rear pinions of transverse axle fastened to one another by a rigid rear cross-piece mounted on the sitting portion adapted to cooperate with the rear racks and at least one actuating member accessible to the user of the seat when he is sitting on said seat and adapted to actuate the rotation of at least one of the two pairs of pinions.
In known embodiments of these seats, the backrest is mounted to pivot on the sitting portion itself which certainly presents the advantage of avoiding any influence of the tilting of the seat on the height-adjustment device, but has also certain drawbacks and in particular the following:
the anchorage of the backrest to the floor of the vehicle passes through the height adjustment mechanism: PA1 this connection is generally insufficiently robust to respond to the relative requirements for the anchoring of the seats and backrests to the floor of the vehicle, in view of the risk of tearing away the latter on sudden deceleration, PA1 the front racks are parallel with the rear racks when the backrest is in its normal driving position, PA1 when the backrest is in its normal driving position, the racks are inclined to the vertical, their top ends being behind with respect to their bottom ends: this measure enables the longitudinal extent of the bearing surface on the sitting portion to be increased automatically during adjustment of the latter downwards, and conversely, PA1 the seat comprises means for angularly fastening the front pinions and the rear pinions: this measure enables the height adjustment of the sitting portion to be ensured by means of a single actuating member, PA1 in a seat according to the preceding paragraph, the angular fastening means comprise two toothed wheels fast respectively to the front pinions and the rear pinions and an endless chain or the like cooperating with these two wheels, PA1 the actuating member of the height adjustment of the seat is a rotary knob associated with automatic locking means for this knob in the resting position, PA1 the control member of the height adjustment device of the sitting portion is the energizing switch of an electric motor, PA1 the seat comprises a reducing gear train inserted between the actuating member and the pinions actuated by this member, so that the rotation by one turn of the member only corresponds to the rotation of a fraction of a turn of the pinions, PA1 the seat comprises at least one helical tension spring of which one end is fixed to the rigid cross piece connecting the axle of the front pinions and the axle of the rear pinions, and of which the other end is fixed to a band wound on a drum fast to one of said pinions, so that this pinion is urged angularly in the direction of the erection of the sitting portion.
the height adjustment relates to the seat as a whole, which does not permit lumbar adjustment to be made through relative vertical movement of the sitting portion with respect to the backrest.
It is an object of the invention to enable these various drawbacks to be overcome.